The present invention relates to a chucking system, designed for high speeds, for detachable connection of two parts, such as is used, for example, for coupling a workpiece or tool carrier, for example in the form of a basic tool mount, and a manipulating means, such as a spindle of a machine tool, or for coupling tool-system modules with one another.
In such chucking systems, which are also known as junction points or disconnection points, the purpose is to clamp the parts to be connected reliably and firmly to one another, exact positional fixation relative to one another of the parts to be connected being ensured by close-fitting surface engagement between a hollow shank of the one part and a receiving portion of the other part. The two parts to be connected are chucked or clamped against one another by the fact that the hollow shank is pulled into the receiving portion against an undercut chucking shoulder by application of chucking members of a chucking means. In the process, a contact pressure is produced between plane faces of the parts to be connected, and so the two parts clamped against one another become fixed in exact axial as well as radial position by the firm connection between the close-fitting faces.
More recently, the hollow-shank chucking system, in which the hollow shank has either cylindrical or conical structure, has become increasingly widely used. When the two parts to be connected are in joined-together condition, the chucking members used to clamp the parts against one another ensure not only that sufficient axial contact pressure is produced, but also that the hollow shank undergoes a certain degree of radial expansion, whereby the accuracy of fit between hollow shank and receiving portion is additionally improved.
As an example, there is proposed in German Patent Application No. 19753663.8 a chucking system for two parts to be connected, such as a tool-system module and a machine-tool spindle, wherein one part has a preferably cylindrical or conical hollow shank and the other part has a corresponding receiving portion for receiving the hollow shank in a precisely fitting relationship. The chucking system comprises a chucking means, disposed concentrically in the receiving portion of the other part, which chucking means extends into the hollow shank of the one part when the two parts are in abutting condition, and is provided with at least two chucking members that can move in opposite directions as well as an actuating means that drives the chucking members, by which actuating means the chucking members can be moved synchronously into and out of engagement with an undercut chucking shoulder of the hollow shank, whereby a contact pressure is produced between plane faces of the two parts to be connected. The chucking members are designed as head portions of elongated chucking elements, which are disposed substantially parallel to the longitudinal axis or axis of rotation of the receiving portion and which are braced axially via retaining portions against an undercut recess of the receiving portion. The chucking elements are connected to one another at their foot portions, this connection being achieved in the preferred embodiment by the fact that the chucking elements are formed by the branches of a U-shaped chucking fork of one-piece structure.
This conventional chucking system is characterized on the one hand by the fact that it works with a minimum of components and on the other hand by the fact that it permits simple, reliable and dimensionally stable coupling of the two parts to be connected without necessitating additional assembly or fastening fixtures.
On the one hand, however, because of the fact that the chucking elements must have a certain degree of elasticity, the design of this chucking system needs a somewhat greater overall axial length of the chucking elements and thus of the chucking means as a whole. On the other hand, since this chucking system can at best be held in the receiving portion via a loose fit with narrow clearance, it is difficult to satisfy the stringent requirements in terms of quality of balance of the overall system comprising machine-tool spindle, chucking means and tool mount with tool, especially at high speeds.
French Patent Application 2754201 A1 discloses a chucking system which is based on the principle of clamping two parts to be connected against one another by a chuck with chucking members. In this chucking system, the chucking members are guided to move slidingly in a radial direction in a carrier member anchored in the receiving portion of the one part and are moved in opposite directions synchronously into or out of engagement with an undercut chucking shoulder in the hollow shank of the other part by an actuator that is also received in the carrier member.
A chucking system is also known from U.S. Pat. No. 5466102. In this chucking system, two loosely disposed or at least not unequivocally fixed clamp-like chucking elements are brought interlockingly into or out of engagement with undercut chucking shoulders in the receiving portion of the one part and in the hollow shank of the other part by an actuator which drives the chucking elements.
The object of the present invention is to provide a chucking system that is optimized in terms of quality of balance of the overall system at high speeds, which system permits, with a minimum of moving parts, simple, reliable and dimensionally stable coupling of the two parts to be connected.
This object is achieved by the chucking system having the features of claim 1.
According to the invention, the chucking system has a carrier member which can be firmly anchored both radially and axially in the receiving portion of a machine-tool spindle, for example, by interference fit, for example, and on which the chucking elements are guided to move slidingly in radial direction. This structural solution has numerous advantages compared with the conventional chucking system. Because the carrier member is firmly anchored in the receiving portion, the number of parts which are movable on the two chucking elements during rotary operation is reduced. Since the chucking elements do not have to be elastically deformable in the manner which was necessary in the conventional chucking system and which was achieved by a relatively large axial length of the chucking elements, the overall axial length of the chucking elements in the inventive chucking system can be much shorter, in turn permitting lighter weight of the chucking elements as well as total weight of the chucking system. The fact that the chucking elements are disposed to move slidingly in radial direction on the carrier member also permits a rotationally symmetric configuration of the chucking elements, which during rotary operation represent the movable parts. These features contribute to a substantial improvement, compared with the conventional chucking system, in terms of positioning reproducibility in chucking and loosening the chucking means of the chucking elements, whereby the scatter of unbalance due to tolerance-related positional scatter of moving parts at high speeds is greatly reduced. Since the reproducibility of the balance condition of the overall system depends substantially on the positional reproducibility of the movable parts of the chucking system as well as the mass and rotational symmetry thereof, the inventive chucking system will satisfy the stringent requirements imposed at high speeds on quality of balance of the overall system, which comprises the two parts to be connected, such as machine-tool spindle and tool mount with tool, as well as the chucking system.
According to the invention, the chucking elements functioning to hold the parts to be connected against one another are designed as relatively robust clamps, which directly span the joint between the parts to be coupled, thus concentrating the flow of force on the smallest space. The efficiency of the chucking means thereby becomes very large, since the chucking means is particularly dimensionally stable by virtue of its geometry, which is preferably barrel-shaped or shell-shaped. In addition, reinforcement of the chucking force of the symmetric chucking elements is achieved as a result of centrifugal force during rotary operation of the chucking system. A further benefit can be seen in a possible increase of surface hardness and thus wear resistance of the chucking elements compared with the limited surface hardness of the chucking elements, which are subjected to bending load, of the conventional chucking system described hereinabove.
The inventive chucking system is further characterized by simple and compact construction, which makes it possible to clamp the parts to be connected against one another in reliable and dimensionally stable manner with a minimum of movable components. Furthermore, since a minimum of moving parts is present in the inventive chucking system, only little friction is produced during movement thereof. In this way an even greater chucking force between the two parts to be connected is achieved.
Further advantageous features of the present invention are subject matter of the dependent claims and/or will become clear from the description hereinafter, in which the inventive chucking system is explained in more detail by means of preferred practical examples.